The number of echoes combined into a single image or image set in multiple echo imaging sequences or echo-train techniques such as rapid acquisition with relaxation enhancement (RARE), fast-spin echo (FSE), and turbo spin-echo (TSE). In RARE imaging, the ETL typically equals the acceleration factor.
As for tooth pain, it is caused by a reaction of the nerves inside a tooth's pulp chamber with the severity dependent upon the type and degree of the stimulus. What follows are some examples of symptoms you may be feeling and their possible causes.
Rec: see your dentist if the sensitivity does not subside within a few weeks, or if your get spontaneous toothache. In brief: 3-4 weeks. A tooth may be sensitive to temperature after the routine dental treatment (filling). Most likely the reason is extensive decay in a proximity to the nerve area. Usually, the sensitivity resolves on its own within a few weeks. Rec: see your dentist if the sensitivity does not subside within a few weeks, or if your get spontaneous toothache. In brief: 3-4 weeks. A tooth may be sensitive to temperature after the routine dental treatment (filling).